Influence of Thermal and Mechanical Factors on the Stressed State of Large Components of Hydrogenerator-Motors

Abstract

The work presented contains a detailed analysis of the existing ultimate power air-cooled hydrogenerator-motor design. It is shown that the umbrella-type hydrogenerator crosspiece perceives dynamic loads caused by forces acting in three planes. At the same time, to take them into account by analytical methods is impossible. In order to perform a three-dimensional calculation, it is necessary to take into account both the thermal and mechanical factors, as well as the specific features of the rolled metal. In the course of solving the problem set out above, taking into account thermal loads, a discrete crosspiece partition into the n-th number of sections is proposed. The convergence criterion for the solution to the inverse problem is based on maintaining the structure overall thermal balance, taking into account the limited accuracy of measuring devices. The main difference of the work was the justification of the choice of permissible stresses, taking into account the presence of bubbles in the metal structure, not exceeding their class of continuity for the selected rolled metal. It is proposed that an 'elementary defect' be introduced into the zone with the lowest safety margins as a circle with geometric data according to the restrictions on continuity. In this case, the correction of the selection of the finite element mesh parameters for the introduced defect is carried out as for the plate with eccentrically located holes. The mesh reduction continues to be carried out until the moment when the difference in the maximum stresses in the same mesh nodes is no more than 0.04%. Mechanical loads are specified in the classical formulation. In the course of the work it was found that the strength reserves of large generator components should be regulated by the quality of the rolled metal used, and the mechanical calculations should take into account thermal factors.